Fiberoptic telecommunications are continually subject to demand for increased bandwidth. One way that bandwidth expansion has been accomplished is through dense wavelength division multiplexing (DWDM) wherein multiple separate data streams exist concurrently in a single optical fiber, with modulation of each data stream occurring on a different channel. Each data stream is modulated onto the output beam of a corresponding semiconductor transmitter laser operating at a specific channel wavelength, and the modulated outputs from the semiconductor lasers are combined onto a single fiber for transmission in their respective channels. The International Telecommunications Union (ITU) presently requires channel separations of approximately 0.4 nanometers, or about 50 GHz. This channel separation allows up to 128 channels to be carried by a single fiber within the bandwidth range of currently available fibers and fiber amplifiers. Improvements in fiber technology together with the ever-increasing demand for greater bandwidth will likely result in smaller channel separation in the future.
The drive towards greater bandwidth has led to use of precision, wavelength-specific DWDM devices that require careful adjustment in order to provide a transmission output at the narrowly separated channel spacings. As tunable elements are configured for narrower channel separation, decreasing component tolerances and thermal fluctuation become increasingly important. In particular, tunable telecommunication transmitter lasers are susceptible to non-optimal positioning of tunable elements due to environmental thermal fluctuation that results in wavelength instability and reduced transmitter output power. There is currently a need for a telecommunication transmitter laser which provides for simple and accurate adjustment of tunable elements to reduce losses and wavelength stability associated with thermal fluctuation and other environmental factors present during laser operation.